1. Field of the Invention
The present invention relates to an image display apparatus, and in particular, to a bonding structure between substrates of an image display apparatus.
2. Description of the Related Art
An image display apparatus using a surface conduction electron-emitting device or a field emission electron-emitting device is known. In this kind of image display apparatus, a substrate in which an image display unit is formed, and a substrate in which an electron-emitting source is formed are arranged oppositely, and structure in which these substrates are bonded through an outer frame is common. Specifically, the outer frame is firmly fixed to one side of a substrate with frit (low melting point glass), the outer frame and another side of the substrate are sealed with a bonding member, and an envelope is formed. As the bonding member, a low melting point metal, such as In (indium), is used. A space between substrates, that is, an interior of the envelope becomes a vacuum apace, and the internal space is sealed from the external with the bonding member.
Usually, although each substrate is formed with glass as a base material, distortion resulting from differences between thermal expansions of substrates may arise in each substrate by factors, such as a temperature difference between one substrate and another substrate which arises at the time of use. When both of the substrates generate a relative position shift, there is a possibility that an electron beam emitted from an electron source may be radiated in a position shifting from a desired position of an image display unit, and may cause deterioration of image quality by this distortion. Then, construction of having reinforcing structure of including an inorganic adhesive and the like, whose principal component is silica alumina, in an outside of an envelope sealed with a bonding member is disclosed in Japanese Patent Application Laid-Open No. 2004-087475. The adhesive (reinforcing structure) is formed between both substrates using a dispenser or the like to fix both substrates firmly. Thereby, the position shift between the substrates resulting from the difference between thermal expansions is prevented.
The reinforcing structure disclosed in Japanese Patent Application Laid-Open No. 2004-087475 is effective in order to prevent a position shift between both substrates, but since the substrates are restrained mutually, distortion resulting from the difference between thermal expansions may arise in the substrates. When the distortion arises in the substrates, even if the position shift between the substrates is prevented, breakdown of the substrate may be caused and there is a possibility of reducing reliability as an image display apparatus.